Isoprene emissions from a Florida scrub oak species grown in ambient and elevated carbon dioxide

The emission of isoprene (2-methyl-1,3-butadiene) by terrestrial vegetation is an important biosphere–atmosphere exchange which significantly impacts tropospheric chemistry. Isoprene emissions from Chapman oak (Quercus chapmanii) grown for over two years in elevated CO₂ levels were measured and compared to emissions from trees grown in ambient CO₂ levels in identical open-topped chambers, and emissions from ambient-grown trees were compared to emissions from trees grown in chamberless control plots. Emission rates were adjusted to 30 μmol m⁻² s⁻¹ of light intensity and 30°C, and standard T-tests were performed to compare emission rates. No significant differences in isoprene emission were found in ambient vs. elevated CO₂ grown trees, while emissions from ambient vs. control trees showed a significant chamber effect.     

Vegetation fire emissions and their impact on air pollution and climate

Gaseous and particulate emissions from vegetation fires substantially modify the atmospheric chemical composition, degrade air quality and can alter weather and climate. The impact of vegetation fire emissions on air pollution and climate has been recognised in the late 1970s. The application of satellite data for fire-related studies in the beginning of the 21th century represented a major break through in our understanding of the global importance of fires. Today the location and extent of vegetation fires, burned area and emissions released from fires are determined from satellite products even though many uncertainties persist. Numerous dedicated experimental and modeling studies contributed to improve the current knowledge of the atmospheric impact of vegetation fires. The motivation of this paper is to give an overview of vegetation fire emissions, their environmental and climate impact, and what improvements can be expected in the near future.     

Short-run allocation of emissions allowances and long-term goals for climate policy

We use economic analysis to evaluate grandfathering, auctioning, and benchmarking approaches for allocation of emissions allowances and then discuss practical experience from European and American schemes. In principle, auctions are superior from the viewpoints of efficiency, fairness, transparency, and simplicity. In practice, auctions have been opposed by important sectors of industry, which argue that carbon pricing without compensation would harm international competitiveness. In the European Union's Emissions Trading System, this concern led to grandfathering that is updated at various intervals. Unfortunately, updating gives industry an incentive to change behavior to influence future allocation. Furthermore, the wealth transferred to incumbent firms can be significantly larger than the extra costs incurred, leading to windfall profits. Meanwhile, potential auction revenues are not available to reduce other taxes. By circumscribing free allocation, benchmarking can target competitiveness concerns, incur less wealth transfer, and provide a strategy consistent with transitioning to auctions in the long run.     

Isoprene emission from tropical tree species

Foliar emission of isoprene was measured in nine commonly growing tree species of Delhi, India. Dynamic flow enclosure technique was used and gas samples were collected onto Tenax-GC/Carboseive cartridges, which were then attached to the sample injection system in the gas chromatograph (GC). Eluting compounds were analysed using a flame ionisation detector (FID). Out of the nine tree species, isoprene emission was found in six species (Eucalyptus sp., Ficus benghalensis, Ficus religiosa, Mangifera indica, Melia azedarach, and Syzygium jambolanum), whereas, in the remaining three tree species (Alstonia scholaris, Azadirachta indica, and Cassia fistula) no isoprene emission was detected or the levels of emission were negligible or below the detection limit (BDL). Among six tree species, the highest hourly emission (10.2 +/- 6.8 microg g(-1) leaf dry weight, average of five seasons) was observed in Ficus religiosa, while minimum emission was from Melia azedarach (2.2 +/- 4.9 microg g(-1) leaf dry weight, average of five seasons). Isoprene emission (average of six species), over five seasons, was found to vary between 3.9 and 8.5 microg g(-1) leaf dry weight during the rainy season. In addition, significant diurnal variation in isoprene emission was observed in each species. The preliminary estimate made in this study on the annual biogenic VOC emission from India may probably be the first of its kind from this part of the world.     

The impacts of combustion emissions on air quality and climate – From coal to biofuels and beyond

Combustion processes have inherent characteristics that lead to the release in the environment of both gaseous and particulate pollutants that have primary and secondary impacts on air quality, human health, and climate. The emissions from the combustion of fossil fuels and biofuels and their atmospheric impacts are reviewed here with attention given to the emissions of the currently regulated pollutant gasses, primary aerosols, and secondary aerosol precursors as well as the emissions of non-regulated pollutants. Fuels ranging from coal, petroleum, liquefied petroleum gas (LPG), natural gas, as well as the biofuels; ethanol, methanol, methyl tertiary-butyl ether (MTBE), ethyl tertiary-butyl ether (ETBE), and biodiesel, are discussed in terms of the known air quality and climate impacts of the currently regulated pollutants. The potential importance of the non-regulated emissions of both gasses and aerosols in air quality issues and climate is also discussed with principal focus on aldehydes and other oxygenated organics, polycyclic aromatic hydrocarbons (PAHs), and nitrated organics. The connection between air quality and climate change is also addressed with attention given to ozone and aerosols as potentially important greenhouse species.     

Isoprene emission capacity for US tree species

Isoprene emission capacity measurements are presented from 18 North American oak (Quercus) species and species from six other genera previously found to emit significant quantities of isoprene. Sampling was conducted at physiographically diverse locations in North Carolina, Central California, and Northern Oregon. Emissions from several sun leaves of each species were measured at or near standard conditions (leaf temperature of 30°C and photosynthetically active radiation of 1000 μmol m⁻² s⁻¹) using environmentally controlled cuvette systems and gas chromatography with reduction gas detectors. Species mean emission capacity ranged from 39 to 158 μg C g⁻¹ h⁻¹ (mean of 86), or 22 to 79 nmol m⁻² s⁻¹ (mean of 44). These rates are 2–28 times higher than those previously reported from the same species, which were summarized in a recent study where isoprene emission rates were assigned based on published data and taxonomy. These discrepancies were attributed to differences in leaf environment during development, measurement technique (branch or plant enclosure versus leaf enclosure), and lack of environmental measurements associated with some of the earlier branch enclosure measurements. Mass-based emission capacities for 15 of 18 oak species, sweetgum (Liquidambar styraciflua), and poplars (Populus trichocarpa and P. deltoides) were within ranges used in current biogenic volatile organic compound (BVOC) emission models, while measured rates for the remaining three oak species, Nyssa sylvatica, Platanus occidentalis, Robinia pseudoacacia, Salix nigra, and Populus hybrids (Populus trichocarpa × P. deltoides) were considerably higher. In addition, mean specific leaf mass of the oak species was 30% higher than assumed in current emission models. Emission rates reported here and in other recent studies support recent conclusions that isoprene emission capacities for sun leaves of high emitting species may be better represented by a value of 100±50 μg C g⁻¹ h⁻¹ during hot summer conditions. We also find that intermediate isoprene emission rates previously suggested for some tree species may not represent their true emission capacities, and that broadleaf plant species may have either low (<1.0 μg C g⁻¹ h⁻¹) or very high (∼100 μg C g⁻¹ h⁻¹) genetic capacity to emit isoprene when mature foliage is exposed to a high ambient temperature and light environment.     

Biogeochemical transformation of greenhouse gas emissions from terrestrial to atmospheric environment and potential feedback to climate forcing

Environmental Science and Pollution Research - Carbon dioxide (CO2) is mainly universal greenhouse gas associated with climate change. However, beyond CO2, some other greenhouse gases (GHGs) like...     

Seasonal variability in CH4 emissions from a landfill in a cool, semiarid climate

Methane exchange with the atmosphere was measured during three seasons at the Rooney Road landfill in Jefferson County, CO. Substantial spatial and temporal variability in exchange rates were observed. Mean fluxes to the atmosphere were 534, 1290, and 538 mg CH4/m2/day, respectively, in the fall of 1994, winter of 1994-1995, and summer of 1995. Median fluxes were 12.42, 8.62, and 5.65 mg CH4/m2/day, respectively, during those seasons. Forty-three of 177 measurements had small negative fluxes, suggesting methanotrophic activity in the landfill cover soils. Despite probable methanotrophic activity in cover soils, landfills without gas collection systems may emit substantial CH4 to the atmosphere, with large spatial and seasonal variability.     

Isoprene emission from tropical trees in Okinawa Island, Japan

This study surveyed isoprene emission from 42 indigenous and exotic tropical trees in subtropic Okinawa, Japan. Of the 42 trees studied, 4 emitted isoprene at a rate in excess of 20 μg g⁻¹ h⁻¹, and 28 showed the rates of 1–10 μg g⁻¹ h⁻¹. The remainder emitted less than 1 μg g⁻¹ h⁻¹. The majority of trees in this study may therefore fall within the lower emitting species. However, species in Moraceae that is indigenous in Okinawa emitted isoprene at relatively higher rates with an average of 14.2 μg g⁻¹ h⁻¹. The highest emission rate of 107.1 μg g⁻¹ h⁻¹ for Ficus virgata yielded the area basis rate of 47.4 nmol m⁻² s⁻¹, which is almost equivalent to the rate of high emitting species. Furthermore, a linear relationship between light intensity and isoprene emission was noted with Ficus virgata up to 1700 μmol m⁻² s⁻¹. These findings may show the potential importance of subtropical areas as sources of isoprene to the atmosphere.     

Elemental carbon and sulfate aerosols over a rural mountain site in the northeastern United States: Regional emissions and implications for climate change

The effect of elemental carbon (EC) on global as well as regional climate forcing is potentially very important. However, the EC data for northeastern U.S. is sparse. Daily EC concentrations, [EC], and [SO₄] were measured in the northeastern U.S. at a regionally representative rural site, Whiteface Mountain (WFM; 44.366°N, 73.903°W, 1.5 km amsl, above mean sea level), New York (NY), for 1997. The air mass origin was determined using 6-h backward in time air trajectories obtained from the Hybrid Single-Particle Lagrangian Integrated Trajectory Model (HYSPLIT 4). [EC] and [SO₄] were highly variable and influenced by synoptic–scale meteorology (rainy vs dry periods). The maximum daily [EC] and [SO₄] were 364 ± 55 and 28,800 ± 3000 ng m^?3, respectively. [EC] and [SO₄] also showed seasonal variations at WFM. Occurrences of high daily [EC] were mainly in spring months, while peak daily [SO₄] concentrations occurred in summer months. This behavior of aerosols is due to the fact that the sources of EC and SO₄ are not the same and also due to the enhanced photochemical activity during summer months that increased the production of SO₄ from SO₂. High [EC] and [SO₄] values were associated with westerly air flow from the industrialized Midwestern U.S. Sector analysis using HYSPLIT 4 air trajectories showed that regions lying between the southwest and northwest of the WFM contributed 81% and 83% of the [EC] and [SO₄], respectively. The monthly net direct radiative forcing for shortwave (SW) due to EC and SO₄ aerosols at the top of the atmosphere (TOA) varied from ?0.05 to ?0.50 W m^?2, with an annual average of ?0.20 ± 0.15 W m^?2 that gives a net cooling effect. Average net radiative forcing at WFM for clear sky is lower than the global average radiative forcing reported by IPCC (Foster and Ramaswamy, 2007).     

Isoprene and monoterpene fluxes measured above Amazonian rainforest and their dependence on light and temperature

Canopy scale emissions of isoprene and monoterpenes from Amazonian rainforest were measured by eddy covariance and eddy accumulation techniques. The peak mixing ratios at about 10 m above the canopy occurred in the afternoon and were typically about 90 ppt_v of α-pinene and 4–5 ppb_v of isoprene. α-pinene was the most abundant monoterpene in the air above the canopy comprising ≈50% of the total monoterpene mixing ratio. Measured isoprene fluxes were almost 10 times higher than α-pinene fluxes. Normalized conditions of 30°C and 1000 μmol m⁻² s⁻¹ were associated with an isoprene flux of 2.4 mg m⁻² h⁻¹ and a β-pinene flux of 0.26 mg m⁻² h⁻¹. Both fluxes were lower than values that have been specified for Amazon rainforests in global emission models. Isoprene flux correlated with a light- and temperature-dependent emission activity factor, and even better with measured sensible heat flux. The variation in the measured α-pinene fluxes, as well as the diurnal cycle of mixing ratio, suggest emissions that are dependent on both light and temperature. The light and temperature dependence can have a significant effect on the modeled diurnal cycle of monoterpene emission as well as on the total monoterpene emission.     

Isoprene and its degradation products as strong ozone precursors in Insubria,Northern Italy

Frequent smog episodes occur during spring, summer, and autumn in Insubria, Northern Italy. On a test site in this area the atmospheric concentration of the photo-oxidants ozone and peroxyacetyl nitrate has been monitored over a year (2000) together with ozone precursors listed in the European Union Air Quality Directive 2002/3/EC, such as nitrous oxides (NO_X) and volatile organic compounds (VOC) including hydrocarbons and carbonyls. The results of this study revealed a strong impact of biogenic isoprene on the air quality.In winter isoprene was detected at the ppt level and correlated with anthropogenic VOC. However, during the growing season isoprene exhibited a distinct diurnal variation with maximum concentrations late in the afternoon reaching up 70 ppbC attributed to strong emissions from the abundant vegetation of broad-leaf deciduous trees in this area. A new HPLC-MS method was developed for the determination of isoprene's primary atmospheric oxidation products methacrolein as its 2,4-dinitrophenylhydrazone and methyl vinyl ketone as an unusual double derivative with 2,4-dinitrophenylhydrazine. Methacrolein and methyl vinyl ketone followed the same diurnal and annual trends as isoprene. The average monthly concentration of isoprene and these products ranged from around 10 ppbC in June, July and September to 20 ppbC in August, which constitutes 15–30% of C₃–C₉ VOCs. The contribution from isoprene photo-oxidation to the ambient air formaldehyde concentrations was also found to be high during this period ranging from 30% to 60% in May, June, July and August.From the atmospheric VOC and NO_X concentrations the local photochemical ozone formation was estimated by the incremental reactivity approach. The calculations showed that in summer isoprene's contribution to the local ozone formation was as high as 50–75%.     

Effects of operating variables on PAH emissions and mutagenicity of emissions from woodstoves.

As part of the Integrated Air Cancer Project, the U.S. Environmental Protection Agency (EPA) has conducted field emission measurement programs in Raleigh, North Carolina, and Boise, Idaho, to identify the potential mutagenic impact of residential wood burning and motor vehicles on ambient and indoor air. These studies included the collection of emission samples from chimneys serving wood burning appliances. Parallel projects were undertaken in instrumented woodstove test laboratories to quantify woodstove emissions during operations typical of in-house usage but under more controlled conditions. Three woodstoves were operated in test laboratories over a range of burnrates, burning eastern oak, southern yellow pine, or western white pine. Two conventional stoves were tested at an altitude of 90 m. One of the conventional stoves and a catalytic stove were tested at an altitude of 825 m. Decreasing burnrate increased total particulate emissions from the conventional stoves while the catalytic stove's total particulate emissions were unaffected. There was no correlation of total particulate emissions with altitude whereas total polynuclear aromatic hydrocarbon (PAH) emissions were higher at the lower altitude. Mutagenicity of the catalytic stove emissions was higher than emissions from the conventional stove. Emissions from burning pine were more mutagenic than emissions from oak.     

Fuel consumption, emissions estimation, and emissions cost estimates using global positioning data

The methodology laid out in this paper shows that typical operational data from vehicle fleets monitored by a global positioning system (GPS) can be used to estimate heavy-duty diesel vehicle (HDDV) emissions, thereby enabling waste managers and governing bodies to internalize the responsibility for socioenvironmental costs traditionally absorbed by external parties. Although municipal solid waste (MSW) collection vehicles are the subjects of this particular study, the methodology presented here can be applied to any fleet of vehicles monitored by GPS. This study indicates that MSW collection trucks may be considerably less fuel efficient in the field than published values for HDDV fuel efficiency suggest. The average fuel efficiency of one MSW collection truck was estimated as 0.90 +/- 0.44 km/L (2.12 +/- 1.03 mi/gal). This same truck would generate approximately 42 metric tons of CO2 equivalents/yr, which is comparable to the greenhouse gas emissions of a large sport utility vehicle driving six times the distance, in town, for a year. In terms of the impacts such emissions have, projections for the monetary cost of emissions are available but highly variable. They suggest that the external monetary costs of emissions range between 6 and 39% of the annual fuel costs for the studied MSW collection truck. The results of this study indicate a need for further research into valuation of the hidden, external costs of emissions, borne by local and global socioecological communities. The possible implications of this result include poorly advised fleet procurement decisions and underestimation of MSW collection fleet emissions.     

Global hexachlorobenzene emissions

Information from a variety of sources has been assembled to give a global picture of hexachlorobenzene (HCB) emissions in the mid 1990s. No single overwhelming source of HCB was identified. The best estimates of global HCB emissions from different categories of sources are as follows: pesticides application - 6500 kg/yr; manufacturing - 9500 kg/yr; combustion - 7000 kg/yr, includes 500 kg from biomass burning. This adds up to total current HCB emissions of approximately 23,000 kg/yr with an estimated range 12,000-92,000 kg/yr. A substantial portion of HCB measured in the atmosphere is thought to come from volatilization of "old" HCB on the soil from past contamination along with unidentified sources. No information on potential sources in developing countries was available.     

Tunnel air quality and vehicle emissions

A general relationship between roadway tunnel air quality and vehicle emissions has been derived. The model includes the effect of pollutant deposition on the tunnel surfaces and dilution from ventilation. The model is applied to air quality measurements of SO₂ and particulates obtained at the Tuscarora Mountain Tunnel. It is found that, if deposition is neglected, SO₂ and sulfate emission factors for both gasoline and Diesel vehicles may be underestimated by ~ 10%. The derived deposition velocities are 0.07cms⁻¹ for SO₂, 0.03cms⁻¹ for sulfate, and ~ 0.001 cms⁻¹ for total suspended particulates and paniculate components (except sulfate). The last value is lower than smooth-surface values quoted for aerosol deposition, and the difference between the last two values presumably reflects the approximations in the model and/or the uncertainty in its input data.